Note 4 - Securities - Securities Available-for-sale (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Securities available-for-sale, amortized costs	$ 635,555	$ 530,075
Securities available-for-sale, gross unrealized gains	11,575	17,170
Securities available-for-sale, gross unrealized losses	5,644	503
Securities available for sale, at fair value	641,486	546,742
US Government Agencies Debt Securities [Member]
Securities available-for-sale, amortized costs	220,372	86,859
Securities available-for-sale, gross unrealized gains	3,062	4,477
Securities available-for-sale, gross unrealized losses	3,243	173
Securities available for sale, at fair value	220,191	91,163
US States and Political Subdivisions Debt Securities [Member]
Securities available-for-sale, amortized costs	196,518	196,435
Securities available-for-sale, gross unrealized gains	4,970	7,778
Securities available-for-sale, gross unrealized losses	2,181	252
Securities available for sale, at fair value	199,307	203,961
Collateralized Mortgage Backed Securities [Member]
Securities available-for-sale, amortized costs	215,661	244,780
Securities available-for-sale, gross unrealized gains	3,284	4,473
Securities available-for-sale, gross unrealized losses	193	78
Securities available for sale, at fair value	218,752	249,175
Corporate Debt Securities [Member]
Securities available-for-sale, amortized costs	3,004	2,001
Securities available-for-sale, gross unrealized gains	259	442
Securities available-for-sale, gross unrealized losses	27
Securities available for sale, at fair value	$ 3,236	$ 2,443

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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